Process for producing optically active 1,3-butanediol by reduction of 4-hydroxy-2-butanone

ABSTRACT

An optically active 1,3-butanediol can be produced by either (1) treating a mixture of 1,3-butanediol enantiomers with a microorganism, which has been optionally treated, capable of asymmetrically assimilating said mixture, or (2) preparing a microorganism, which has been optionally treated, capable of asymmetrically reducing 4-hydroxy-2-butanone, and collecting optically active 1,3-butanediol.

This application is a divisional of application Ser. No. 07/964,264,filed on Oct. 21, 1992, which in turn is a divisional of applicationSer. No. 07/449,929, filed on Dec. 7, 1989, and now issued as U.S. Pat.No. 5,219,757.

FIELD OF INDUSTRIAL APPLICATION

The present invention relates to a process for producing opticallyactive 1,3-butanediol with a microorganism.

Optically active 1,3-butanediol is an important starting material forvarious medicines such as antibiotics.

Prior Art

Known processes for producing optically active 1,3-butanediol include(1) a process wherein a chemically synthesized mixture of 1,3-butanediolracemates is optically resolved with an optical resolving agent (cf.Japanese Patent Laid-Open No. 191631/1986) and (2) a process wherein itis produced from 4-hydroxy-2-butanone by asymmetric synthesis with aRaney nickel catalyst treated with an optically active compound [cf.Japanese Patent Laid-Open No. 204187/1983 and Bull. Chem. Soc. Jpn., 53,1356 to 1360 (1980)]. However, both the processes (1) and (2) have adefect that expensive optical resolving agent and catalyst must be usedand, in addition, the product obtained by the process (2) has a lowoptical purity. Under these circumstances, it is demanded to establish aprocess for producing optically active 1,3-butanediol having a highoptical purity in an economically advantageous and convenient manner.

Disclosure of the Invention

The present invention provides a process for producing optically active1,3-butanediol which comprises either (1) treating a mixture of1,3-butanediol enantiomers with a microorganism, which has beenoptionally treated, capable of asymmetrically assimilating said mixture,or (2) preparing a microorganism, which has been optionally treated,capable of asymmetrically reducing 4-hydroxy-2-butanone, and collectingoptically active 1,3-butanediol.

The present invention involves (1) asymmetric assimilation and (2)reduction as follows:

(1) a process for producing optically active 1,3-butanediol whichcomprises treating a mixture of 1,3-butanediol enantiomers with amicroorganism, which has been optionally treated, capable ofasymmetrically assimilating said mixture and collecting optically active1,3-butanediol remaining intact, and

(2) a process for producing optically active 1,3-butanediol whichcomprises treating 4-hydroxy-2-butanone with a microorganism, which hasbeen optionally treated, capable of asymmetrically reducing4-hydroxy-2-butane into either (R)-1,3-butanediol or (S)-1,3-butanedioland collecting the (R)-1,3-butanediol or (S) -1,3-butanediol thusformed.

The present invention will now be described in detail by referring tothese two processes.

(1) Asymmetric assimilation

After intensive investigations made for the purpose of getting amicroorganism usable for producing optically active 1,3-butanediolhaving a high optical purity by asymmetric assimilation, the inventorshave found that a microorganism selected from among those belonging tothe genera Brevibacterium, Candida, Enterobacter, Geotrichum,Klebsiella, Lodderomyces, Pseudomonas, Rhodotorula, Saccharomyces,Saccharomycopsis, Sterigmatomyces and Trichosporon is capable ofasymmetrically assimilating a mixture of 1,3-butanediol enantiomers toleave (R)-1,3-butanediol intact, and that a microorganism selected fromamong those belonging to the genera Agrobacterium, Azotobacter,Bacillus, Brettanomyces, Candida, Citrobacter, Corynebacterium, Dekkera,Endomyces, Erwinia, Hansenula, Issatchenkia, Klebsiella, Kluyveromyces,Geotrichum, Micrococcus, Mycobacterium, Pachysolen, Paracoccus, Pichia,Protaminobacter, Pseudomonas, Saccharomyces, Saccharomycopsis,Selenotila, Serratia, Stephanoascus and Xanthomonas is capable ofasymmetrically assimilating a mixture of 1,3-butanediol enantiomers toleave (S)-1,3-butanediol intact.

The microorganism usable in the present invention may be any of thosebelonging to the genus Brevibacterium, Candida, Enterobacter,Geotrichum, Klebsiella, Lodderomyces, Pseudomonas, Rhodotorula,Saccharomyces, Saccharomycopsis, Sterigmatomyces or Trichosporon capableof asymmetrically assimilating a mixture of 1,3-butanediol enantiomersto leave (R)-1,3-butanediol intact or any of those belonging to thegenus Agrobacterium, Azotobacter, Bacillus, Brettanomyces, Candida,Citrobacter, Corynebacterium, Dekkera, Endomyces, Erwinia, Hansenula,Issatchenkia, Klebsiella, Kluyveromyces, Geotrichum, Micrococcus,Mycobacterium, Pachysolen, Paracoccus, Pichia, Protaminobacter,Pseudomonas, Saccharomyces, Saccharomycopsis, Selenotila, Serratia,Stephanoascus or Xanthomonas capable of asymmetrically assimilating amixture of 1,3-butanediol enantiomers to leave (S) -1,3-butanediolintact.

The microorganisms capable of asymmetrically assimilating a mixture of1,3-butanediol enantiomers to leave (R)-1,3-butanediol intact includeBrevibacterium iodinum IFO 3558, Candida rugosa IFO 1364, Candidaparapsilosis IFO 0640, Candida parapsilosis IFO 0708, Candidaparapsilosis IFO 1396, Enterobacter cloacac ATCC 7256, Geotrichumcandidum IFO 4601, Geotrichum candidum IFO 5767, Geotrichum candidum IFO5368, Geotrichum rectangulatum JCM 1750, Geotrichum klebahnii JCM 2171,Geotrichum fermentans JCM 2467, Geotrichum capitatum JCM 3908,Geotrichum eriense JCM 3912, Klebsiella pneumoniae IFO 12019,Lodderomyces elongisporus IFO 1676,Pseudomonas diminuta IFO 12697,Rhodotorula glutinis IFO 0395, Saccharomyces cerevisiae AHU 3402,Saccharomycopsis lipolytica ITO 1550, Sterigmatomyces elviae DSM 70852,Trichosporon cutaneum IFO 1198 and Trichosporon capitatum IFO 0743.

The microorganisms capable of asymmetrically assimilating a mixture of1,3-butanediol enantiomers to leave (S)-1,3-butanediol intact includeAgrobacterium radiobacter IFO 12664, Azotobacter chroococcum IFO 12994,Bacillus brevis IFO 3331, Bacillus cereus AHU 1707, Bacillus cereus AHU1355, Bacillus sphaericus IFO 3525, Bacillus sphaericus IFO 3341,Bacillus subtilis IFO 3007, Bacillus subtilis IFO 3037, Brettanomycesabstines DSM 70726, Candida cariosilignicola DSM 2148, Candida kefyr(Beijerinck) DSM 70073, Candida krusei (Castellani) DSM 70025, Candidasucciphila DSM 2149, Candida utilis IFO 0639, Candida utilis IFO 0626,Citrobacter freundii AHU 1534, Corynebacterium glutamicum ATCC 13032,Corynebacterium michiganense IFO 13762, Dekkera bruxellensis IFO 1590,Endomyces decipien IFO 0102, Erwinia carotovora subsp. carotovora IFO3830, Geotrichum fragrans JCM 1749, Hansenula anomala DSM 70130,Hansenula minuta DSM 70274, Hansenula subpelliculosa IFO 0808, Hansenulawickerhamii DSM 70280, Hansenula wingei DSM 10281, Issatchenkiascutulata var. scutulata IFO 10070, Klebsiella pneumoniae IFO 12059,Kluyveromyces drosophilarum IFO 1012, Kluyveromyces lactis IFO 1267,Kluyveromyces lactis IFO 1903, Micrococcus luteus IFO 3333, Micrococcusroseus IFO 3764, Mycobacterium smegmatis IFO 3153, Pachysolentannophilus IFO 1007, Paracoccus denitrificans IFO 12442, Pichiacellobiosa DSM 2147, Pichia farinosa IFO 1163, Pichia heedii IFO 10020,Pichia heedii IFO 10019, Pichia lindnerii DSM 70718, Pichia opuntiaevar. thermotolerans IFO 10026, Pichia opuntiae var. thermotolerans IFO10025, Pichia pastoris DSM 70382, Pichia querquum DSM 70386, Pichiasargentensis DSM 70388, Pichia trehalophia DSM 70391, Protaminobacterruber IAM 1081, Pseudomonas acidovorans IFO 13582, Pseudomonas diminutaIFO 12697, Pseudomonasfluorescens IFO 12055, Pseudomonas fluorescens IFO3081, Pseudomonas putida IFO 3738, Saccharomyces cerevisiae IAM 0216,Saccharomycopsis fibuligera IFO 0103, Selenotila peltata DSM 70579,Serratia marcescens IAM 1105, Stephanoascus ciferrii IFO 1854,Xanthomonas maltophilia IFO 12690 and Xanthomonas oryzae IAM 1657.

Each strain may be either a wild type, a variant or a recombinantobtained by genetic engineering such as cell fusion or generecombination.

Microorganisms having IFO numbers assigned thereto are described in theList of Cultures, 8th ed., vol. 1 (1988) published by the Institute forFermentation, Osaka (IFO) and available therefrom. Those having AHUnumbers are described in the Catalogue of Cultures, 4th ed. (1987)published by Japan Federation of Culture Collection (JFCC) and availablefrom the Faculty of Agriculture, Hokkaido University. Those having ATCCnumbers are described in the Catalogue of Bacteria Phages rDNA Vectors,16th ed. (1985) published by American Type Culture Collection (ATCC) andavailable therefrom. Those having JMC numbers are described in theCatalogue of Strains, 3rd ed. (1986) published by Japan Cellection ofMicroorganisms, RIKEN and available therefrom. Those having IAM numbersare available from the Institute of Applied Microbiology, the Universityof Tokyo. Those having DSM numbers are described in the Catalog ofStrains (1983) published by Deutsche Sammlung yon Mikroorganismen (DSM)and available therefrom.

The following strains were deposited at the Institute for Fermentation,Osaka, 17-85 Jusohonmachi 2-chome, Yodogawa-ku, Osaka Japan asindicated:

Kluveromyces lactis was deposited on Dec. 9, 1964 under the accessionnumber IFO 1267;

Pichia opuntiae was deposited on Mar. 19, 1982 under the accessionnumber IFO 10025;

Geotricum candidum was deposited in 1952 under the accession number5368;

Candida utilis was deposited in 1954 under the accession number IFO0639;

Candida parapsilosis was deposited on Jun. 1, 1967 under the accessionnumber IFO 1369.

The above deposits were made as to afford a permanently viable stock of,and ready public accessibility to, the indicated strains so as to allowpractice of the invention described in this patent document. Samples ofeach of these strains will be made available to the public (1) for theterm of 30 years, (2) for five years after the last request for a sampleof a deposited strain or (3) for the enforceable life of any patentwhich issues from this document, whichever is longer.

The culture medium used in the present invention is not particularlylimited so far as the microorganism can grow in or on it. The carbonsource may be any of carbon nutrients for growing the microorganism. Thecarbon sources include, for example, saccharides such as glucose,fructose, sucrose and dextrin; alcohols such as sorbitol, ethanol andglycerol; organic acids such as fumaric, citric, acetic and propionicacids and salts thereof; hydrocarbons such as paraffin; and mixtures ofthem. The nitorgen sources include inorganic and organic nitrogenouscompounds such as ammonium salts of inorganic acids, e.g., ammoniumchloride, ammonium sulfate and ammonium phosphate; ammonium salts oforganic acids, e.g., ammonium fumarate and ammonium citrate; meatextract; yeast extract; corn steep liquor; casein hydrolyzate; urea aswell as mixtures thereof. Furthermore various nutritional sourcescommonly used in the culture of microorganisms, such as inorganic salts,trace metal salts and vitamins, may be appropriately mixed and used inthe present invention. In addition, materials effective in promoting thegrowth of the microorganism, in elevating the productivity of the targetcompound of the present invention or in maintaining the pH value of themedium on the desired level may be added, if required.

The pH value of the medium may be adjusted to 3.0 to 9.5, preferably 4to 8. The culture may be carried out at a temperature of 20° to 45° C.,preferably 25° to 37° C., either aerobically or anaerobically underconditions suitable for the growth of the microorganism for 5 to 120hours, preferably about 12 to 72 hours.

The asymmetric assimilation may be effected by using the culture mediumas such. Alternately, the cells may be separated by, for example,centrifugation, optionally washed and resuspended in a buffer solutionor water. Then the mixture of 1,3-butanediol enantiomers may be added tothe suspension thus obtained. In this reaction, it is sometimespreferable to add a carbon source such as glucose or sucrose to themedium to thereby supply energy. The cells may be used as such in theform of viable cells. Alternately, they may be ground, treated withacetone or lyophilized. These cells, which have been optionally treated,may be immobilized prior to the use by a conventional method such as thepolyacrylamide gel, sulfur-containing polysaccharide gel (such ascarrageenan gel), alginic acid gel or agar gel method. Furthermore, anenzyme obtained from said treated cells by combining known methods maybe used in the present invention.

The mixture of 1,3-butanediol enantiomers may be added either at once atthe initiation of the reaction or in portions in the course of thereaction either as such, dissolved in water or an inert organic solventor dispersed in, for example, a surfactant.

The reaction may be conducted at a pH value of 3 to 10, preferably 5 to9, at 10° to 60° C., preferably 20° to 40° C. for 1 to 120 hours with orwithout stirring. A prolonged reaction time causes a reduction in theamount of the remaining 1,3-butanediol, though an optically active1,3-butanediol having a high optical purity can be obtained in thiscase. The concentration of the substrate may range preferably from about0.1 to 10%, though it is not restricted thereto.

The optically active 1,3-butanediol remaining intact after the reactioncan be easily collected by extracting the reaction mixture, from whichthe cells have been optionally separated, with an organic solvent andpurifying the extract by, for example, distillation or columnchromatography.

(2) Reduction

After intensive investigations made for the purpose of getting amicroorganism usable for producing optically active 1,3-butanediolhaving a high optical purity by asymmetric reduction, the inventors havefound that a microorganism selected from among those belonging to thegenera Ambrosiozyma, Bacillus, Candida, Citrobacter, Corynebacterium,Hansenula, Issatchenkia, Kluyveromyces, Pichia, Protaminobacter,Pseudomonas, Rhodotorula, Selenotila, Schizosaccharomyces, Stephanoascusand Xanthomonas is capable of asymmetrically reducing4-hydroxy-2-butanone into (R)-1,3-butanediol, and that a microorganismselected from among those belonging to the genera Brevibacterium,Candida, Geotrichum, Klebsiella, Lodderomyces, Saccharomycopsis andTrichosporon is capable of asymmetrically reducing 4-hydroxy-2-butanoneinto (S)-1,3-butanediol.

The microorganism usable in the present invention may be any of thosebelonging to the genus Ambrosiozyma, Bacillus, Candida, Citrobacter,Corynebacterium, Hansenula, Issatchenkia, Kluyveromyces, Pichia,Protaminobacter, Pseudomonas, Rhodotorula, Selenotila,Schizosaccharomyces, Stephanoascus or Xanthomonas capable ofasymmetrically reducing 4-hydroxy-2-butanone into (R)-1,3-butanediol orany of those belonging to the genus Brevibacterium, Candida, Geotrichum,Klebsiella, Saccharomycopsis or Trichosporon capable of asymmetricallyreducing 4-hydroxy-2-butanone into (S)-1,3-butanediol.

The microorganisms capable of forming (R)-1,3-butanediol from4-hydroxy-2-butanone include Ambrosiozyma cicatricosa IFO 1846, Bacillussereus AHU 1355, Bacillus subtilis IFO 3007, Candida cariosilignicolaDSM 2148, Candida arborea IAM 4147, Candida kefyr (Beijerinck) DSM70073, Candida krusei (Castellani) DSM 70075, Candida guilliermondii IAM4412, Candida succiphila DSM 2149, Candida utilis IFO 0639, Candidautilis IFO 0626, Candida utilis IAM 4277, Citrobacter freundii AHU 1534,Corynebacterium michiganense IFO 13762, Hansenula polymorpha ATCC 26012,Hansenula minuta DSM 70274, Hansenula subpelliculosa IFO 0808, Hansenulafabianii IFO 1254, Hansenula wickerhamii DSM 70280, Hansenula wingei DSM10281, Issatchenkia scutulata var. scutulata IFO 10070, Issatchenkiascutulata var. scutulata IFO 10069, Kluyveromyces drosophilarum IFO1012, Kluyveromyces lactis IFO 1267, Kluyveromyces lactis IFO 1903,Pichia cellobiosa DSM 2147, Pichia heedii IFO 10019, Pichia heedii IFO10020, Pichia lindnerii DSM 70718, Pichia opuntiae var. thermotoleransIFO 10025, Pichia pastoris DSM 70382, Pichia trehalophia DSM 70391,Protaminobacter ruber IAM 1081, Pseudomonas diminuta IFO 12697,Pseudomonas fluorescens IFO 3081, Pseudomonas putida IFO 3738,Rhodotorula rubra IFO 0383, Selenotila peltata DSM 70579,Schizosaccharomyces pombe IFO 0363, Stephanoascus ciferrii IFO 1854 andXanthomona maltophilia IFO 12690. The microorganisms capable of forming(S)-1,3-butanediol from 4-hydroxy-2-butanone include Brevibacteriumiodinum IFO 3558, Candida rugosa IFO 1664, Candida parapsilosis IFO0640, Candida parapsilosis IFO 0708, Candida parapsilosis IFO 1396,Geotrichum candidum IFO 4601, Geotrichum candidum IFO 5767, Geotrichumcandidum IFO 5368, Geotrichum rectangulatum JCM 1750, Geotrichumklebanoii JCM 2171, Geotrichum fermentans JCM 2467, Geotrichum capitatumJCM 3908, Geotrichum eriense JCM 3912, Klebsiella pneumoniae IFO 12019,Lodderomyces elongisporus IFO 1676, Saccharomycopsis lipolytica ITO1550, Trichosporon cutaneum IFO 1198 and Trichosporon capitatum IFO0743.

Each strain may be either a wild type, a variant or a recombinantobtained by genetic engineering such as cell fusion or generecombination.

Microorganisms having IFO numbers assigned thereto are described in theList of Cultures, 8th ed., vol. 1 (1988) published by the Institute forFermentation, Osaka (IFO) and available therefrom. Those having AHUnumbers are described in the Catalogue of Cultures, 4th ed. (1987)published by Japan Federation of Culture Collection (JFCC) and availablefrom the Faculty of Agriculture, Hokkaido University. Those having JCMnumbers are described in the Catalogue of Strains, 3rd ed. (1986)published by Japan Collection of Microorganisms, RIKEN and availabletherefrom. Those having ATCC numbers are described in the Catalogue ofBacteria Phages rDNA Vectors, 16th ed. (1985) and the Catalogue ofFungi/Yeast, 17th ed. (1987) published by American Type CultureCollection (ATCC) and available therefrom. Those having DSM numbers aredescribed in the Catalog of Strains (1983) published by DeutscheSammlung von Mikroorganismen (DSM) and available therefrom. Those havingIAM numbers are available from the Institute of Applied Microbiology,the University of Tokyo.

The culture medium used in the present invention is not particularlylimited so far as the microorganism can grow in or on it. The carbonsource may be any of carbon nutrients for growing the microorganism. Thecarbon sources include, for example, saccharides such as glucose,fructose, sucrose and dextrin; alcohols such as sorbitol, ethanol andglycerol; organic acids such as fumaric, citric, acetic and propionicacids and salts thereof; hydrocarbons such as paraffin; and mixtures ofthem. The nitrogen sources include inorganic and organic nitrogenouscompounds such as ammonium salts of inorganic acids, e.g. ammoniumchloride, ammonium sulfate and ammonium phosphate; ammonium salts oforganic acids, e.g. ammonium fumarate and ammonium citrate; meatextract; yeast extract; corn steep liquor; casein hydrolyzate; urea aswell as mixtures thereof. Furthermore various nutritional sourcescommonly used in the culture of microorganisms, such as inorganic salts,trace metal salts and vitamins, may be appropriately mixed and used inthe present invention. In addition, materials effective in promoting thegrowth of the microorganism, in elevating the productivity of the targetcompound of the present invention or in maintaining the pH value of themedium on the desired level may be added, if required.

The pH value of the medium may be adjusted to 3.0 to 9.5, preferably 4to 8. The culture may be carried out at a temperature of 20° to 45° C.,preferably 25° to 37° C., either aerobically or anaerobically underconditions suitable for the growth of the microorganism for 5 to 120hours, preferably about 12 to 72 hours.

The reduction may be effected by using the culture medium as such.Alternately, the cells may be separated by, for example, centrifugation,optionally washed and resuspended in a buffer solution or water. Then4-hydroxy-2-butanone may be added to the suspension thus obtained. Inthis reaction, it is sometimes preferable to add a carbon source such asglucose or sucrose to the medium to thereby supply energy. The cells maybe used as such in the form of viable cells. Alternately, they may beground, treated with acetone or lyophilized. These cells, which havebeen optionally treated, may be immobilized prior to the use by aconventional method such as the polyacrylamide gel, sulfur-containingpolysaccharide gel (such as carrageenan gel), alginic acid gel or agargel method. Furthermore, an enzyme obtained from said treated cells bycombining known methods may be used in the present invention.

The 4-hydroxy-2-butanone may be added either at once at the initiationof the reaction or in portions in the course of the reaction either assuch, dissolved in water or an inert organic solvent or dispersed in,for example, a surfactant.

The reaction may be conducted at a pH value of 3 to 9, preferably 5 to8, at 10° to 60° C., preferably 20° to 40° C. for 1 to 120 hours with orwithout stirring. The concentration of the substrate may preferablyrange from about 0.1 to 10%, though it is not restricted thereby.

The optically active 1,3-butanediol thus formed may be readily collectedby extracting the reaction mixture, from which the cells may beoptionally separated, with an organic solvent and purifying the extractby, for example, distillation or column chromatography.

EXAMPLES

The following Examples will further illustrate the present invention,which by no means limit the present invention.

In the following Examples, 1,3-butanediol in the reaction liquid mixturewas easily determined according to gas chromatography [column: Thermon3000, (2 m), 130° C.] and the optical purity was determined byacetylating optically active 1,3-butanediol obtained by the reactionwith acetyl chloride by an ordinary method and subjecting it to highperformance liquid chromatography with an optical resolution column[column: Chiral cel OB (mfd. by Daicel Chemical Industries, Ltd.),solvent: n-hexane/2propanol=19:1, wavelength:. 220 nm, flow rate: 0.5ml/min) [retention time: 15 min for (S)-enantiomer and 19.3 min for(R)-enantiomer].

Example 1

    ______________________________________                                        <Microorganism-producing culture medium>                                      ______________________________________                                               glucose        1.0%                                                           yeast extract  0.3%                                                           peptone        0.5%                                                           1,3-butanediol 0.5%                                                           K.sub.2 HPO.sub.4                                                                            0.1%                                                           MgSO.sub.4.7H.sub.2 O                                                                        0.05%                                                                         pH 7.2                                                  ______________________________________                                    

100 ml of the microorganism-producing culture medium having theabove-described composition was put in a 500-ml Sakaguchi flask. Aftersterilization followed by inoculation with a microorganism shown inTable 1, the shaking culture was conducted at 30° C. for 48 h. Then themicroorganism was separated by centrifugation and washed withphysiological saline once to give viable cells.

Then 50 ml of distilled water was put in a 500-ml Sakaguchi flask, inwhich the microorganism obtained as described above was suspended. 0.5 gof racemic 1,3-butanediol was added to the suspension and the reactionwas conducted under reciprocal shaking at 30° C. for 48 h.

After the completion of the reaction followed by removal of the cells bycentrifugation, the supernatant liquid was saturated with sodiumchloride and extracted with 50 ml of ethyl acetate. The ethyl acetatelayer was analyzed according to gas chromatography to determine theamount of remaining 1,3-butanediol.

Thereafter ethyl acetate was dehydrated with anhydrous Glauber's salt.After removing the solvent, a syrup was obtained. The syrup wasacetylated with acetyl chloride by an ordinary method and the productwas dissolved in a solvent and analyzed according to high performanceliquid chromatography to determine the absolute configuration and theoptical purity of obtained 1,3-butanediol.

The results are shown in Table 1.

Example 2

Candida parapsilosis IFO 1396 was put in a 10-l jar fermenter containing5 l of the same culture medium as that used in Example 1 and culturedunder stirring at 250 r.p.m. at 30° C. for 24 h. The flow rate was 0.5v.v.m. After the completion of the culture, the cells were collected byfiltration, washed with 5 l of water and suspended in 500 ml of water.10 g of racemic 1,3-butanediol was added to the suspension and themixture was stirred at 30° C. for 48 h to conduct the reaction. Afterthe completion of the reaction, the cells were removed bycentrifugation. The obtained supernatant liquid was saturated withsodium chloride and extracted with 250 ml of ethyl acetate twice. Theethyl acetate layer was dehydrated with anhydrous Glauber's salt. Afterremoving the solvent under reduced pressure, 4.2 g of a syrup wasobtained. The syrup was distilled under reduced pressure to give 4.0 gof colorless transparent (R)-1,3-butanediol. The product had a specificrotatory power [α]_(D) ²⁰ of -28° (C=1 in EtOH), an absoluteconfiguration of the (R)-enantiomer and an optical purity determined byHPLC analysis of 96% e.e.

Example 3

Geotrichum candidum IFO 4601 was cultured and the reaction andextraction were conducted in the same manner as that of Example 2 togive 4.0 g of a syrup. 1,3-Butanediol thus obtained was analyzed toreveal that it had an absolute configuration of the (R)-enantiomer andan optical purity of 90% e.e.

Example 4

Candida utilis IFO 0639 was cultured and the reaction and extractionwere conducted in the same manner as that of Example 2 to give 4.9 g ofa syrup. 1,3-Butanediol thus obtained was analyzed to reveal that it hadan absolute configuration of the (S)-enantiomer and an optical purity of92% e.e.

Example 5

Pichia opuntiae var. thermotolerans IFO 10025 was cultured and thereaction and extraction were conducted in the same manner as that ofExample 2 to give 3.7 g of a syrup. 1,3-Butanediol thus obtained wasanalyzed to reveal that it had an absolute configuration of the(S)-enantiomer and an optical purity of 97% e.e.

                                      TABLE 1                                     __________________________________________________________________________                       Amount of     Optical                                                         remaining     purity of                                                       1,3-butanediol                                                                       Absolute                                                                             1,3-butanediol                               Microorganism      (mg/ml)                                                                              configuration                                                                        (% e.e.)                                     __________________________________________________________________________    Brevibacterium iodinum IFO 3558                                                                  2.4    R      51                                           Candida rugosa IFO 1364                                                                          6.4    R      36                                           Candida parapsilosis IFO 0640                                                                    5.8    R      50                                           Candida parapsilosis IFO 0708                                                                    5.3    R      55                                           Candida parapsilosis IFO 1396                                                                    4.0    R      98                                           Enterobacter cloacae ATCC 7256                                                                   6.4    R      32                                           Geotrichum candidum IFO 4601                                                                     1.9    R      94                                           Geotrichum candidum IFO 5767                                                                     2.4    R      80                                           Geotrichum candidum IFO 5368                                                                     2.6    R      98                                           Geotrichum rectangulatum JCM 1750                                                                4.0    R      74                                           Geotrichum klebahnii JCM 2171                                                                    5.0    R      58                                           Geotrichum fermentans JCM 2467                                                                   4.0    R      88                                           Geotrichum capitatum JCM 3908                                                                    5.5    R      40                                           Geotrichum eriense JCM 3912                                                                      6.1    R      23                                           Klebsiella pneumoniae IFO 1209                                                                   5.5    R      30                                           Lodderomyces elongisporus                                                                        4.9    R      72                                           IFO 1676                                                                      Pseudomonas, diminuta IFO 12697                                                                  6.3    R      33                                           Rhodotorula glutinis IFO 0395                                                                    6.0    R      34                                           Saccharomyces cerevisiae                                                                         6.6    R      31                                           AHU 3402                                                                      Saccharomycopsis lipolytica                                                                      5.1    R      68                                           IFO 1550                                                                      Sterigmatomyces elviae                                                                           5.6    R      47                                           DSM 70852                                                                     Trichosporon cutaneum IFO 1198                                                                   4.8    R      67                                           Trichosporon capitatum IFO 0743                                                                  5.5    R      35                                           Agrobacterium radiobacter                                                                        5.5    S      40                                           IFO 12664                                                                     Azotobacter chroococcum                                                                          6.4    S      21                                           IFO 12994                                                                     Bacillus brevis IFO 3331                                                                         6.2    S      27                                           Bacillus cereus AHU 1707                                                                         7.5    S      41                                           Bacillus cereus AHU 1355                                                                         6.0    S      49                                           Bacillus sphaericus IFO 3525                                                                     6.0    S      42                                           Bacillus sphaericus IFO 3341                                                                     6.3    S      29                                           Bacillus subtilis IFO 3007                                                                       5.9    S      54                                           Bacillus subtilis IFO 3037                                                                       7.0    S      25                                           Brettanomyces abstines                                                                           6.8    S      29                                           DSM 70726                                                                     Candida cariosilignicola                                                                         5.2    S      70                                           DSM 2148                                                                      Candida kefyr (Beijerinck)                                                                       5.9    S      47                                           DSM 70073                                                                     Candida krusei (Castellani)                                                                      6.1    S      47                                           DSM 70075                                                                     Candida succiphila DSM 2149                                                                      6.5    S      50                                           Candida utilis IFO 0639                                                                          4.3    S      91                                           Candida utilis IFO 0626                                                                          4.9    S      76                                           Citrobacter freundii AHU 1534                                                                    5.1    S      69                                           Corynebacterium glutamicum                                                                       6.9    S      21                                           ATCC 13032                                                                    Corynebacterium michiganense                                                                     5.0    S      73                                           IFO 13762                                                                     Dekkera bruxellensis IFO 1590                                                                    5.9    S      32                                           Endomyces decipien IFO 0102                                                                      6.8    S      21                                           Erwinia carotovora subsp.                                                                        6.5    S      21                                           carotovora IFO 3830                                                           Geotrichum fragrans JCM 1749                                                                     6.0    S      31                                           Hansenula anomala DSM 70130                                                                      2.4    S      26                                           Hansenula minuta DSM 70274                                                                       4.6    S      58                                           Hansenula subpelliculosa                                                                         4.4    S      71                                           IFO 0808                                                                      Hansenula wickerhamii DSM 70280                                                                  5.1    S      47                                           Hansenula wingei DSM 10281                                                                       5.8    S      59                                           Issatchenkia scutulata var.                                                                      6.8    S      46                                           scutulata IFO 10070                                                           Klebsiella pneumonias IFO 12059                                                                  7.0    S      24                                           Kluyveromyces drosophilarum                                                                      5.7    S      36                                           IFO 1012                                                                      Kluyveromyces lactis IFO 1267                                                                    4.9    S      76                                           Kluyveromyces lactis IFO 1903                                                                    5.1    S      57                                           Micrococcus luteus IFO 3333                                                                      7.0    S      21                                           Micrococcus roseus IFO 3764                                                                      6.5    S      22                                           Mycobacterium smegmatis                                                                          3.5    S      30                                           IFO 1012                                                                      Pachysolen tannophilus IFO 1007                                                                  6.4    S      25                                           Paracoccus denitrificans                                                                         6.4    S      29                                           IFO 12442                                                                     Pichia cellobiosa DSM 2147                                                                       6.3    S      56                                           Pichia farinosa IFO 1163                                                                         6.2    S      23                                           Pichia heedii IFO 10020                                                                          6.5    S      40                                           Pichia heedii IFO 10019                                                                          6.1    S      45                                           Pichia lindnerii DSM 70718                                                                       7.1    S      40                                           Pichia opuntiae var.                                                                             4.5    S      95                                           thermotolerans IFO 10026                                                      Pichia opuntiae var.                                                                             4.4    S      97                                           thermotolerans IFO 10025                                                      Pichia pastoris DSM 70382                                                                        6.0    S      59                                           Pichia querquum DSM 70386                                                                        5.0    S      25                                           Pichia sargentensis DSM 70388                                                                    3.9    S      28                                           Pichia trehalophia DSM 70391                                                                     6.7    S      48                                           Protaminobacter ruber IAM 1081                                                                   6.2    S      46                                           Pseudomonas adidovorans                                                                          7.0    S      23                                           IFO 13582                                                                     Pseudomonas diminuta IFO 12697                                                                   4.2    S      51                                           Pseudomonas fluorescens                                                                          5.5    S      52                                           IFO 12055                                                                     Pseudomonas fluorescens                                                                          6.2    S      40                                           IFO 3081                                                                      Pseudomonas putida IFO 3738                                                                      5.0    S      75                                           Saccharomyces cerevisiae                                                                         6.6    S      24                                           IAM 0216                                                                      Saccharomycopsis fibuligera                                                                      5.3    S      22                                           IFO 0103                                                                      Selenotila peltata DSM 70579                                                                     5.6    S      45                                           Serratia marcescens IAM 1105                                                                     6.9    S      23                                           Stephanoascus ciferrii IFO 1854                                                                  4.2    S      78                                           Xanthomonas maltophilia                                                                          5.1    S      41                                           IFO 12690                                                                     Xanthomonas oryzae IAM 1657                                                                      6.2    S      34                                           __________________________________________________________________________

Example 6

100 ml of a YM medium comprising 0.3% of yeast extract, 0.3% of maltextract, 0.5% of peptone and 2% of glucose and having a pH of 6.0 in thecase of yeast strains or 100 ml of a YMP medium comprising 2% ofglucose, 0.5% of yeast extract, 0.3% of peptone, 0.3% of meat extract,0.2% of (NH₄)₂ HPO₄ and 0.1% of KH₂ PO₄ and having a in the case ofbacterial strains was put in a 500-ml Sakaguchi flask. Aftersterilization followed by the inoculation with a microorganism shown inTable 2, reciprocal shaking culture was conducted at 30° C. for 48 h.Cells were separated by centrifugation and washed once withphysiological saline to give viable cells.

50 ml of distilled water was put in a 500-ml Sakaguchi flask and theviable cells obtained above was suspended therein. 5 g of glucose wasadded to the suspension. After the reciprocal shaking at 30° C. for 10min, 0.5 g of 4-hydroxy-2-butanone was added thereto and the reactionwas conducted under the reciprocal shaking at 30° C. for 20 h.

After the completion of the reaction, the cells were removed bycentrifugation and the supernatant liquid thus obtained was saturatedwith sodium chloride. After extraction with 50 ml of ethyl acetate, theethyl acetate layer was analyzed according to gas chromatography todetermine the reaction yield.

Then the ethyl acetate layer was dehydrated with anhydrous Glauber'ssalt and the solvent was removed to give a syrup. The syrup wasacetylated with acetyl chloride and dissolved in a solvent. The absoluteconfiguration and optical purity of the product were determinedaccording to high performance liquid chromatography. The results areshown in Table 2.

Example 7

Candida utilis IAM 4275 was put in a 10-l jar fermenter containing 5 lof a YM medium and cultured under stirring at 250 r.p.m. at 30° C. for48 h. The flow rate was 0.5 v.v.m.

After the completion of the culture, the cells were collected byfiltration, washed with 5 l of water and suspended in 500 ml of water. 5g of 4-hydroxy-2-butanone and 50 g of glucose were added to thesuspension and the mixture was stirred at 30° C. for 24 h to conduct thereaction.

After the completion of the reaction, the cells were removed bycentrifugation. The obtained supernatant liquid was saturated withsodium chloride and extracted with 250 ml of ethyl acetate twice. Theethyl acetate layer was analyzed according to gas chromatography toreveal that the reaction yield was 85%.

Then the ethyl acetate layer was dehydrated with anhydrous Glauber'ssalt. After removing the solvent under reduced pressure, 4.0 g of asyrup was obtained. The syrup was distilled to give colorlesstransparent (R)-1,3-butanediol.

The absolute configuration and optical purity of the obtained1,3-butanediol determined by HPLC were that of the (R)-enantiomer and94% e.e., respectively.

Example 8

Kluyveromyces lactis IFO 1267 was cultured and the reaction andextraction were conducted in the same manner as that of Example 7 togive 4.5 g of a syrup. The reaction yield was 95%, and the absoluteconfiguration and optical purity of the obtained 1,3-butanediol werethat of the (R)-enantiomer and 92% e.e., respectively.

Example 9

Candida parapsilosis IFO 1396 was cultured and the reaction andextraction were conducted in the same manner as that of Example 7 togive 3.5 g of a syrup. The reaction yield was 64%, and the absoluteconfiguration and optical purity of the obtained 1,3-butanediol werethat of the (S) -enantiomer and 98% e .e., respectively.

Example 10

Geotrichum candidam IFO 4601 was cultured and the reaction andextraction were conducted in the same manner as that of Example 7 togive 3.2 g of a syrup. The reaction yield was 78% and the absoluteconfiguration and optical purity of the obtained 1,3-butanediol werethat of the (S)-enantiomer and 88% e.e., respectively.

                                      TABLE 2                                     __________________________________________________________________________                         Reaction     Optical                                                          yield                                                                              Absolute                                                                              purity                                      Microorganism        (%)  configuration                                                                         (% e.e.)                                    __________________________________________________________________________    Ambrosiozyma cicatricosa IFO 1846                                                                  46   R       48                                          Bacillus cereus AHU 1355                                                                           25   R       55                                          Bacillus subtilis IFO 3007                                                                         23   R       64                                          Candida cariosilignicola DSM 2148                                                                  34   R       85                                          Candida arborea IAM 4147                                                                           37   R       99                                          Candida kefyr (Beijerinck) DSM 70073                                                               43   R       54                                          Candida krusei (Castellani) DSM 70075                                                              41   R       59                                          Candida succiphila DSM 2149                                                                        57   R       64                                          Candida utilis IFO 0639                                                                            86   R       95                                          Candida utilis IFO 0626                                                                            76   R       93                                          Candida utilis IAM 4277                                                                            82   R       95                                          Citrobacter freundii AHU 1534                                                                      54   R       69                                          Corynebacterium michiganense IFO 13762                                                             46   R       73                                          Hansenula polymorpha ATCC 26012                                                                    96   R       85                                          Hansenula minuta DSM 70274                                                                         34   R       45                                          Hansenula subpelliculosa IFO 0808                                                                  56   R       76                                          Hansenula fabianii IFO 1254                                                                        26   R       67                                          Hansenula wickerhamii DSM 70280                                                                    43   R       45                                          Hansenula wingei DSM 10281                                                                         47   R       64                                          Issatchenkia scutulata var. scutulata                                                              45   R       99                                          IFO 10070                                                                     Issatchenkia scutulata IFO 10069                                                                   50   R       93                                          Kluyveromyces drosophilarum IFO 1012                                                               43   R       42                                          Kluyveromyces lactis IFO 1267                                                                      98   R       93                                          Kluyveromyces lactis IFO 1903                                                                      88   R       92                                          Pichia cellokiesa DSM 2147                                                                         76   R       79                                          Pichia heedii IFO 10019                                                                            35   R       86                                          Pichia heedii IFO 10020                                                                            24   R       81                                          Pichia lindnerii DSM 70718                                                                         20   R       78                                          Pichia opuntiae var. thermotolerans                                                                54   R       94                                          IFO 10025                                                                     Pichia pastoris DSM 70382                                                                          58   R       87                                          Pichia trehalophia DSM 70391                                                                       56   R       83                                          Protaminobacter ruber IAM 1081                                                                     43   R       62                                          Pseudomonas diminuta IFO 12697                                                                     42   R       65                                          Pseudomonas fluoroscens IFO 3081                                                                   53   R       76                                          Pseudomonas putida IFO 3738                                                                        53   R       85                                          Stephanoascus ciferrii IFO 1854                                                                    40   R       60                                          Rhodotorula rubra IFO 0383                                                                         16   R       53                                          Selenotila peltata DSM 70579                                                                       25   R       62                                          Schizosaccharomyces pombe IFO 0363                                                                 25   R       35                                          Xanthomonas maltophilia IFO 12690                                                                  34   R       59                                          Brevibacterium iodinum IFO 3558                                                                    56   S       85                                          Candida rugosa IFO 1364                                                                            53   S       63                                          Candida parapsilosis IFO 0640                                                                      55   S       90                                          Candida parapsilosis IFO 0708                                                                      51   S       94                                          Candida parapsilosis IFO 1396                                                                      60   S       98                                          Geotrichum candidam IFO 4601                                                                       78   S       88                                          Geotrichum candidam IFO 5767                                                                       45   S       90                                          Geotrichum candidam IFO 5368                                                                       65   S       93                                          Geotrichum rectangulatum JCM 1750                                                                  45   S       81                                          Geotrichum klebahnii JCM 2171                                                                      54   S       75                                          Geotrichum fermentans JCM 2467                                                                     48   S       77                                          Geotrichum capitatum JCM 3908                                                                      44   S       81                                          Geotrichum eriense JCM 3912                                                                        51   S       68                                          Klebsiella pneumoniae IFO 1209                                                                     32   S       30                                          Lodderomyces elongisporus IFO 1676                                                                 62   S       70                                          Saccharomycopsis lipolytica IFO 1550                                                               61   S       65                                          Trichosporon cutaneum IFO 1198                                                                     64   S       80                                          Trichosporon capitatum IFO 0743                                                                    25   S       37                                          __________________________________________________________________________

We claim:
 1. A process for producing optically active 1,3 butandiol,which comprises treating 4-hydroxy-2-butanone with a microorganism,capable of asymmetrically reducing 4-hydroxy-2-butanone into either(R)-1,3-butanediol or (S)-1,3-butanediol, said microorganism beingselected from the group consisting of:Ambrosiozyma cicatricosa Bacilluscereus Bacillus subtilis Candida cariosilignicola Candida arboreaCandida kefyr (Beijerinck) Candida krusei (Castellani) Candidasucciphila Candida utilis Citrobacter freundii Corynebacteriummichiganense Hansenula polymorpha Hansenula minuta Hansenulasubpelliculosa Hansenula fabianii Hansenula wickerhamii Hansenula wingeiIssatchenkia scutulata var. scutulata Issatchenkia scutulataKluyveromyces drosophilarum Kluyveromyces lactis Pichia cellobiosaPichia heedii Pichia lindneri Pichia opuntiae var. thermotolerans Pichiapastoris Pichia trehalophia Protaminobacter ruber Pseudomonas diminutaPseudomonas fluorescens Pseudomonas putida Stephanoascus ciferriiRhodotorula rubra Selenotila peltata Schizosaccharomyces pombeXanthomonas maltophilia Brevibacterium iodinum Candida rugosa Candidaparapsilosis Geotrichum candidum Geotrichum rectangulatum Geotrichumklebahnii Geotrichum fermentans Geotrichum capitatum Geotrichum erienseKlebsiella pneumoniae Lodderomyces elongisporus Saccharomycopsislipolytica Trichosporon cutaneum and Trichosporon capitatumand (2)collecting the (R)-1,3-butanediol or (S)-1,3-butanediol thus formed. 2.A process according to claim 1, wherein said microorganism is capable ofreducing 4-hydroxy-2-butanone to (R)-1,3-butanediol and saidmicroorganism is selected from the group consisting of:Ambrosiozymacicatricosa Bacillus cereus Bacillus subtilis Candida cariosilignicolaCandida arborea Candida kefyr (Beijerinck) Candida krusei (Castellani)Candida succiphila Candida utilis Citrobacter freundii Corynebacteriummichiganense Hansenula polymorpha Hansenula minuta Hansenulasubpelliculosa Hansenula fabianii Hansenula wickerhamii Hansenula wingeiIssatchenkia scutulata var. scutulata Issatchenkia scutulataKluyveromyces drosophilarum Kluyveromyces lactis Pichia cellobiosaPichia heedii Pichia lindneri Pichia opuntiae var. thermotolerans Pichiapastoris Pichia trehalophia Protaminobacter ruber Pseudomonas diminutaPseudomonas fluorescens Pseudomonas putida Stephanoascus ciferriiRhodotorula rubra Selenotila peltata Schizosaccharomyces pombe andXanthomonas maltophilia.
 3. A process as according to claim 1, whereinsaid microorganism is capable of reducing 4-hydroxy-2-butanone to(S)-1,3-butanediol and said microorganism is selected from the groupconsisting of:Brevibacterium iodinum Candida rugosa Candida parapsilosisGeotrichum candidum Geotrichum rectangulatum Geotrichum klebahniiGeotrichum fermentans Geotrichum capitatum Geotrichum eriense Klebsiellapneumoniae Lodderomyces elongisporus Saccharomycopsis lipolyticaTrichosporon cutaneum and Trichosporon capitatum.
 4. A process forproducing optically active 1,3 butandiol, which comprises treating4-hydroxy-2-butanone with a microorganism, capable of asymmetricallyreducing 4-hydroxy-2-butanone into either (R)-1,3-butanediol or(S)-1,3-butanediol, said microorganism being selected from the groupconsisting of:

    ______________________________________                                        Ambrosiozyma cicatricosa                                                                           IFO       1846                                           Bacillus cereus      AHU       1355                                           Bacillus subtilis    IFO       3007                                           Candida kefyr (Beijerinck)                                                                         DSM       70073                                          Candida krusei (Castellani)                                                                        DSM       70075                                          Citrobacter freundii AHU       1534                                           Corynebacterium michiganense                                                                       IFO       13762                                          Hansenula polymorpha ATCC      26012                                          Hansenula minuta     DSM       70274                                          Hansenula subpelliculosa                                                                           IFO       0808                                           Hansenula fabianii   IFO       1254                                           Hansenula wickerhamii                                                                              DSM       70280                                          Hansenula wingei     DSM       70281                                          Issatchenkia scutulata var.                                                                        IFO       10070                                          scutulata                                                                     Issatchenkia scutulata                                                                             IFO       10069                                          Kluyveromyces drosophilarum                                                                        IFO       1012                                           Pichia cellobiosa    DSM       2147                                           Pichia heedii        IFO       10019                                          Pichia heedii        IFO       10020                                          Pichia pastoris      DSM       70382                                          Pichia trehalophia   DSM       70391                                          Protaminobacter ruber                                                                              IAM       1081                                           Pseudomanas diminuta IFO       12697                                          Pseudomanas fluorescens                                                                            IFO       3081                                           Pseudomonas putida   IFO       3738                                           Stephanoascus ciferrii                                                                             IFO       1854                                           Rhodotorula rubra    IFO       0383                                           Selenotila peltata   DSM       70579                                          Schizosaccharomyces pombe                                                                          IFO       0363                                           Xanthomonas maltophilia                                                                            IFO       12690                                          Brevibacterium iodinum                                                                             IFO       3558                                           Candida rugosa       IFO       1364                                           Candida parapsilosis IFO       0640                                           Candida parapsilosis IFO       0708                                           Geotrichum candidum  IFO       4601                                           Geotrichum candidum  IFO       5767                                           Geotrichum rectangulatum                                                                           JCM       1750                                           Geotrichum klebahnii JCM       2171                                           Geotrichum fermentans                                                                              JCM       2467                                           Geotrichum capitatum JCM       3908                                           Geotrichum eriense   JCM       3912                                           Klebsiella pneumoniae                                                                              IFO       12009                                          Lodderomyces elongisporus                                                                          IFO       1676                                           Saccharomycopsis lipolytica                                                                        IFO       1550                                           Trichosporon cutaneum                                                                              IFO       1198 and                                       Trichosporon capitatum                                                                             IFO       0743                                           ______________________________________                                    

and (2) collecting the (R)-1,3-butanediol or (S)-1,3-butanediol thusformed.
 5. A process according to claim 4, wherein said microorganism iscapable of reducing 4-hydroxy-2-butanone to (R)-1,3-butanediol and saidmicroorganism is selected from the group consisting of:

    ______________________________________                                        Ambrosiozyma cicatricosa                                                                           IFO       1846                                           Bacillus cereus      AHU       1355                                           Bacillus subtilis    IFO       3007                                           Candida cariosilignicola                                                                           DSM       2148                                           Candida kefyr (Beijerinck)                                                                         DSM       70073                                          Candida krusei (Castellani)                                                                        DSM       70075                                          Candida succiphila   DSM       2149                                           Candida utilis       IFO       0626                                           Citrobacter freundii AHU       1534                                           Corynebacterium michiganense                                                                       IFO       13762                                          Hansenula polymorpha ATCC      26012                                          Hansenula minuta     DSM       70274                                          Hansenula subpelliculosa                                                                           IFO       0808                                           Hansenula fabianii   IFO       1254                                           Hansenula wickerhamii                                                                              DSM       70280                                          Hansenula wingei     DSM       10281                                          Issatchenkia scutulata var. scutulata                                                              IFO       10070                                          Issatchenkia scutulata                                                                             IFO       10069                                          Kluyveromyces drosophilarum                                                                        IFO       1012                                           Kluyveromyces lactis IFO       1903                                           Pichia cellobiosa    DSM       2147                                           Pichia heedii        IFO       10019                                          Pichia heedii        IFO       10020                                          Pichia pastoris      DSM       70382                                          Pichia trehalophia   DSM       70391                                          Protaminobacter ruber                                                                              IAM       1081                                           Pseudomonas diminuta IFO       12697                                          Pseudomonas fluorescens                                                                            IFO       3081                                           Pseudomonas putida   IFO       3738                                           Stephanoascus ciflerrii                                                                            IFO       1854                                           Rhodotorula rubra    IFO       0383                                           Selenotila peltata   DSM       70579                                          Schizosaccharomyces pombe                                                                          IFO       0363 and                                       Xanthomonas maltophilia                                                                            IFO      
 12690.                                         ______________________________________                                    


6. A process as according to claim 4, wherein said microorganism iscapable of reducing 4-hydroxy-2-butanone to (S)-1,3-butanediol and saidmicroorganism is selected from the group consisting of:

    ______________________________________                                        Brevibacterium iodinum                                                                             IFO       3558                                           Candida rugosa       IFO       1364                                           Candida parapsilosis IFO       0640                                           Candida parapsilosis IFO       0708                                           Geotrichum candidum  IFO       4601                                           Geotrichum candidum  IFO       5767                                           Geotrichum rectangulatum                                                                           JCM       1750                                           Geotrichum klebahnii JCM       2171                                           Geotrichum fermentans                                                                              JCM       2467                                           Geotrichum capitatum JCM       3908                                           Geotrichum eriense   JCM       3912                                           Klebsiella pneumoniae                                                                              IFO       1209                                           Lodderomyces elongisporus                                                                          IFO       1676                                           Saccharomycopsis lipolytica                                                                        IFO       1550                                           Trichosporon cutaneum                                                                              IFO       1198 and                                       Trichosporon capitatum                                                                             IFO      
 0743.                                          ______________________________________                                    


7. A process according to claim 4, wherein said microorganism has beenimmobilized.
 8. A process according to claim 4, wherein said reductionis accomplished by an enzyme isolated from said microorganism.
 9. Aprocess according to claim 4, wherein said microorganism is collected,washed and resuspended in water or a buffer.
 10. A process according toclaim 4, wherein said microorganism is collected, washed, treated withacetone and lyophilized.
 11. A process according to claim 10, whereinsaid microorganism is further immobilized.
 12. A process for producingoptically active 1,3-butanediol, which comprises:(a) centrifuging,washing and resuspending in a buffer solution cells of microorganismsselected from the group consisting of:

    ______________________________________                                        Candida utilis     IFO       0639                                             Candida parapsilosis                                                                             IFO       1396                                             Geotrichum candidum                                                                              IFO       5368                                             Kluyveromyces lactis                                                                             IFO       1267 and                                         Pichia opuntiae var.                                                                             IFO       10025                                            thermotolerans                                                                ______________________________________                                    

(b) treating 4-hydroxy-2-butanone with this solution; and (c) recoveringeither (R)-1,3-butanediol or (S)-1,3-butanediol.
 13. The processaccording to claim 12, further comprising immobilizing said cells insaid buffer solution.